Method and apparatus for the production of metallic coatings on electrically nonconducting substances by the thermal vaporization of metals in vacuo



March 16, 1937.

L. A. SOMMER 2,074,281 METHOD AND APPARATUS FOR THE PRODUCTION OFMETALLIC COATINGS ON ELECTRICALLY NONCONDUCTING SUBSTANCES BY THETHERMAL VAPORIZATION OF METALS IN VACUO Filed July 6, 1954 O Q a y 3 943 4% lllwulllll 19' Patented Mar. 16, 1937 UNITED STATES PATENT OFFICEDUCTION STANCES BY THE OF METALLIC COATINGS ,ELECTRICALLY NONCONDUCTINGON SUB- THERMAL VAPORIZA- TION OF METALS IN VACUO Ludwig August" Sommer,Berlin-Dahlem, Germany Application July 6, 1934, Serial No. 734,041 InGermany July 13, 1933 3 Claims.

The invention relates to the production of metallic coatings onelectrically non-conducting substances, such as paper, textile fabrics,leather, celluloid and the like by the thermal vaporization of metals invacuo. For this purpose vacua of 3 x 10- to about 10- mm. of mercuryhave been employed. k

I have found that in the thermal vaporization of the coating metal andthe deposition of the same on electrically non-conducting materials asubstantial improvement in the metallic deposits is obtained in ahighvacuum.

A vacuum of say 10- to 10- mm. of mercury is meant as a high vacuum inthis case. The deposits obtained by thermal metallic vaporization in ahigh vacuum on electrically non-conducting materials of all kinds, suchas paper, wood, linen, wool, cotton, silk, artificial silk, jute, hempor other textile fabrics, glass. porcelain, earthenware, leather, hidesand skins, artificial masses and so forth, are distinguished by greateruniformity, greater tenacity or adhesive power, chemical purity, andfreedom from oxidation, good electrical conductivity and metallic highpolish.

I have further found that these coatings obtained by thermalvaporization of metals in a high vacuum are very well adapted to serveas a basis for further metallic deposits obtained electrolytically.

The invention also comprises an apparatus specially designed forcarrying out the said process and which is illustrated in an example ofconstruction in the accompanying drawing. Further features of theinvention will appear from the description of the apparatus.

The drawing shows a longitudinal section of a vacuum chamber, which inthe construction illustrated is formed by a section of a seamless pipeI, both ends of which are capable of being tightlyclosed by covers 2 and3. According to the invention, steel or a bronze free from pores ispreferably employed as constructional material for the chamber, thewalls inside, and if desired also outside, being-tinned (tin coating 4).This construction has proved to be particularly advantageous in enablingthe high vacuum used in the chamber to be maintained.

The evacuation of the chamber is done through the pipe connection l6. Onthe bottom of the (Cl. ill-12.2)

chamber, a receptacle or vessel 5, consisting of insulating material orceramic material, is arranged in known manner in the wall of which anelectric resistance heater 6 is provided. The molten metal 1 iscontained in the receptacle 5. 5

The web of material 8 to be metallized is slowly wound from one roller 9on to another roller l0, and during this operation is carried past inthe proximity of the opening of the receptacle 5.

According to the invention the material 8 to be 10 metallized isstrongly cooled at the place on which the metal atoms impinge. In theconstruction illustrated in the drawing, the cooling is effected by theguide II for the web of material being formed by a receptacle whichprojects into the 15 chamber and is partly filled with liquid air l2lMetallic deposits which are particularly dense and adherent are obtainedaccording to the invention by an acceleration being imparted to thevaporized metal atoms on their way from the 0 melted mass 1 to the web8. This is effected by an electrode, for instance, an annular electrodel3, being inserted between the receptacle 5 and the material. Theopposite electrode I4 is situated on the bottom of the receptacle 5. Byapplying a high voltage, of, for example, several thousand volts, whichis supplied from the source of current IS, a difference in potential iscreated between the melted mass 7 and the annular electrode i3, whichdiiference of potential on the positive charging of the annularelectrode and negative charging of the melted metal causes a greatacceleration of the vaporized negatively charged metal atoms.Consequently, the vaporized metal strikes the material to be metallized35 with great force and metallic coatings which are particularly firmlyadherent and dense are produced.

I claim:-

1. A process for producing metallic coatings which consists in melting ametal, evaporating said metal under a high vacuum of about 10- mm. orbelow of mercury, creating a potential difference between a positiveelectrode arranged above the surface of the metal and a negativeelectrode connected to the metal, maintaining the said potentialdifference for accelerating the ions of the metal vapour and collectingthe metal vapour under the said high vacuum on a surface.

2. An apparatus for producing metallic coatmeans for feeding a surfaceto be metallized over the base end of the flask, means for melting ametal, a positive electrode arranged between the surface of the metal tobe melted and the base end of the flask, a negative electrode connectedto the metal to be melted, and means for placing the vessel under a highvacuum.

LUDWIG AUGUST SOMMER.

